This invention relates to drainage apparatus, and more particularly to apparatus for draining fluids such as blood from a body cavity and for the reuse of such fluids. The invention is especially concerned with such an apparatus that will allow a patient to generate the required vacuum for inspiration but that will automatically protect a patient from being exposed to dangerously high vacuum levels.
Blood recovered from a patient's body cavity (autologous blood) offers significant advantages over blood from other humans (homologous blood). Autologous blood reduces the risk of adverse reactions and transmission of infectious disease, has near normal oxygen carrying capacity and pH, conserves blood supplies, provides a readily available source of compatible blood; and provides cost savings. For these reasons, the practice of reinfusing autologous blood, known as autotransfusion, is expanding rapidly.
Autotransfusion may be used in the emergency room setting to recover blood lost through chest trauma; in the operating room setting to recover blood shed during surgery; or in the intensive care setting to recover shed mediastinal blood following cardiac or other surgery.
Various devices have been developed to drain and collect fluids such as blood from a body cavity for subsequent auto-infusion. The following U.S. Pat. Nos. illustrate prior art developments in drainage and/or auto-infusion devices.
U.S. Pat. No. 3,559,647 Bidwell et al PA1 U.S. Pat. No. 3,683,913 Kurtz et al PA1 U.S. Pat. No. 3,853,128 Kurtz et al PA1 U.S. Pat. No. 4,018,224 Kurtz et al PA1 U.S. Pat. No. 4,112,948 Kurtz et al PA1 U.S. Pat. No. 4,443,220 Hauer et al PA1 U.S. Pat. No. 4,540,413 Russo PA1 U.S. Pat. No. 4,605,400 Kurtz et al
In U.S. Pat. No. 3,853,128, for example, there is disclosed a drain apparatus of one piece unitary construction. The device includes a collection chamber for collecting fluids from a body cavity, a water seal chamber for preventing passage of air from the atmosphere into the body cavity, and a manometer chamber for regulating the degree of vacuum in the system. The collection chamber is connected by a thoracotomy tube to the patient's pleural cavity. The device is connected to a suction pump and the amount of liquid in the manometer chamber determines the degree of vacuum imposed. A valve mechanism is provided in the water seal chamber to permit the outflow of gases from the apparatus in the event of a sudden increase in pressure in the device, such as may occur when the patient coughs.
One difficulty encountered with the prior art devices is that no provision is made for autoinfusing simultaneously with draining. A device which would allow autotransfusion simultaneously with draining would have significant advantages over prior art devices, especially in the emergency room and operating room settings. Elimination of time-consuming intervening steps between collection, transfer of blood, and autotransfusion would streamline the autotransfusion tasks of medical personnel and enhance the utility of autotransfusion.
The prior art drainage devices generally cannot be used to simultaneously collect blood from the pleural cavity and autotransfuse, because there is no provision in prior art devices for automatic regulation of negative pressure during autotransfusion. During autotransfusion, as fluid exits the collection chamber, remaining fluid volume drops and pressure negativity increases. It is important to maintain pressure negativity within a relatively narrow range to keep bleeding to a minimum and to prevent damage to intrathoracic tissue. It is also important to maintain pressure negativity within a relatively narrow range in order to prevent water from being siphoned out of the water seal chamber and into the collection chamber. Loss of water in this manner would render the water seal useless as a one way valve for air.
One approach to the solution to this problem is to provide a chamber comprising a collapsable bag whose volume can change as required. See U.S. Pat. No. 4,443,220. Such blood bags may be removed from the drainage device when full and placed on a stand to effect reinfusion, but these devices are incapable of simultaneous drainage and reinfusion. Another approach is to provide a mechanical pressure regulating mechanism in communication with a collection chamber which functions to regulate the subatmospheric pressure in the collection chamber independent of the chamber's effective volume. See U.S. Pat. No. 4,548,413. Such mechanical pressure regulating mechanisms are costly and often unreliable.
The relative underpressures suitable for drainage of the thoracic cavity are in the range of several centimeters of water, representing a pressure difference of well under 0.01 atmospheres. However, the drainage tube from a patient may itself have a significant volume; as a result, the process of "stripping" the tube to clear its lumen by forcing blockages along the tube may introduce substantial fluctuation in pressure into the drainage vessel. Further, the placing of a separate collection vessel in the suction drainage system alters system volume. For these reasons, the combination of known drainage devices with a separate fluid collection chamber for collecting a portion of fluid for reinfusion cannot be expected to maintain a uniform suction at the desired low level. Moreover, known systems for fluid collection are not adapted for simultaneously both draining fluids and transferring the desired fluids into the circulatory system.
While it is necessary to allow the patient to draw as much vacuum pressure as is required during normal and deep inspiration without breaking the water seal, currently available fluid recovery systems allow dangerously high levels of vacuum to accumulate within the patient's chest. This is due to the ratio of water volume at the bottom of the water seal and the valve design at the top of this chamber. In recognizing this extremely dangerous situation designers have added a manual mechanical Push button type valve to the chest drain in order to release accumulated vacuum pressure. Known chest drain systems, therefore, use float valves to maintain high vacuum in the collection chamber and manually operated vents to release high vacuum. There are, however, problems associated with known manual vents.
One problem associated with manual venting of high accumulated vacuum is that because of restrictions in the height of the calibrated water seal column, the operator of the manual vent has no idea how high the vacuum pressure actually is. Additionally the operator will have to visually observe the water seal float valve position and water level, that is the amount of water on top of the valve, and guess at whether or not excess vacuum is present in the system. Then, only if it is known that the patient's chest tubes have been recently stripped or milked, will the operator assume that there is a dangerous level of vacuum. These known manual venting systems do not give any inherent indication that high vacuum is present other than that of the presence of water on top of the float valve.
Another problem with manual venting of excess vacuum is that to alleviate this vacuum the operator must push down on the manual push button atmospheric valve to allow atmospheric pressure to relieve the closed system vacuum. Such a procedure can take the operator anywhere from 30-60 seconds and requires that constant pressure be kept on the manual vent valve. Additionally, the operator must carefully observe and coordinate the level of the water seal with the release of pressure on the manual valve. If the operator does not carefully observe and coordinate the release of pressure on the manual vent, the patient's intrathoracic vacuum could be lowered to a dangerously low level such as atmospheric pressure. Since the purpose of any water seal chest drain system is to restore and maintain a minimum level of vacuum to the patient's chest following surgery, failure to stop manual venting at the proper moment, will cause serious clinical event known as pneumothorax. Such an event will require immediate physician attention.
It is, therefore, an object of the present invention to provide a fluid recovery system having an improved float valve in the water seal chamber that provides automatic controlled release of accumulated high vacuum beyond that required for patient inspiration.
It is also an object of the invention to provide a reliable, easily used, inexpensive, and disposable drainage device capable of simultaneous collection and auto-infusion of collected fluid and which regulates subatmospheric suction pressure during both drainage and auto-infusion while minimizing introduction of ambient air to the collected and reinfused fluids.
It is yet another object of the present invention to provide a versatile device which functions effectively intra-operatively as a suction powered drainage device, as well as post-operatively as a device for draining the plural and mediastinal cavities without inducing excessive bleeding or fluid exudation and without damaging intrathoracic tissue.